FIX issue redefining location in UPDATE only when the name of the location differs

Solving the issue raised at http://stackoverflow.com/questions/24431177/ge-orion-context-broker-when-we-make-an-update-of-the-entity-does-not-allow-us
Aren these questions already answered in https://forge.fi-ware.org/plugins/mediawiki/wiki/fiware/index.php/Publish/Subscribe_Broker_-_Orion_Context_Broker_-_User_and_Programmers_Guide#Geolocation_capabilities documentation?